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posted by mrpg on Saturday September 22 2018, @03:59PM   Printer-friendly
from the read-and-find-out dept.

How long does a quantum jump take?

It was one of the crucial experiments in quantum physics: when light falls on certain materials, electrons are released from the surface. Albert Einstein was the first to explain this phenomenon in 1905, when he spoke of "light quanta" -- the smallest units of light that we call photons today.

In tiny fractions of a second, an electron of the material absorbs a photon, "jumps" into another state and leaves the surface. This "photoelectric effect" is so fast that until now it has mostly been regarded as instantaneous -- as a sudden change of state, from one moment to the next. However, new measurement methods are so precise that it has now become possible to observe such a process and to measure its duration precisely. A team from the Vienna University of Technology, together with research groups from Garching, Munich and Berlin, determined the duration of the photoelectric effect at a tungsten surface. The results were published in the journal Nature.


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  • (Score: 3, Funny) by WizardFusion on Saturday September 22 2018, @04:16PM

    by WizardFusion (498) Subscriber Badge on Saturday September 22 2018, @04:16PM (#738577) Journal

    Well a Quantum Leap [next-episode.net] is about 5 seasons and 97 episodes

  • (Score: 4, Informative) by Anonymous Coward on Saturday September 22 2018, @04:27PM (1 child)

    by Anonymous Coward on Saturday September 22 2018, @04:27PM (#738581)

    The article sez: in tungsten, it takes 45 attoseconds for the outermost electrons and 100 attoseconds for the innermost.

    • (Score: 0) by Anonymous Coward on Saturday September 22 2018, @06:48PM

      by Anonymous Coward on Saturday September 22 2018, @06:48PM (#738618)

      So about 8x10^26 plank times?

      And is this the time that it takes, or the time it takes to measure?

  • (Score: 5, Interesting) by Tara Li on Saturday September 22 2018, @04:57PM (1 child)

    by Tara Li (6248) on Saturday September 22 2018, @04:57PM (#738591)

    Now, the question that comes to mind is this: is the duration of these events in proportion to the "distance" traveled in this jump, and how does it relate to C?

    Now, I'm aware that electrons do not "orbit" in the same manner as planets orbiting the Sun, so "distance" is not quite the right word, but that the probability waveform is shaped such that the most likely position is at some particular surface around the nucleus (or even in the nucleus) and that its extent before reaching an arbitrate cut-off grows as the electron gains energy, so the "speed" here might be the velocity of the changes to the waveform as it evolves from one extent to the other - aka, how fast does the boundary of that cut-off expand?

    And what does it mean if this transition happens faster than C would allow for - aka, information is transferred from the point of interaction to the full extent of the waveform faster than it should be? (All this, of course, colored by the cloud of virtual particles that surrounds every real particle. Does that sound as whacked to everyone else as it does to me?)

    • (Score: 0) by Anonymous Coward on Saturday September 22 2018, @06:08PM

      by Anonymous Coward on Saturday September 22 2018, @06:08PM (#738613)

      Makes sense to me. Sounds fascinating. I doubt it would lead to FTL travel or communication. Probably would be yet another discontinuity that occurs in the realm of the very small.

      Though who knows. Experiments that try to pinpoint the scale necessary for quantum phenomena to break down are interesting. Superconductors come to mind.

  • (Score: 1, Interesting) by Anonymous Coward on Saturday September 22 2018, @08:22PM (7 children)

    by Anonymous Coward on Saturday September 22 2018, @08:22PM (#738641)

    QM is incompatible with GR (discrete vs continuous universes). Also, photons do not experience time according to GR. So from whose perspective are they measuring this time?

    • (Score: 2) by opinionated_science on Saturday September 22 2018, @08:33PM (1 child)

      by opinionated_science (4031) on Saturday September 22 2018, @08:33PM (#738643)

      quite. time is reversible. What prevents practical reversion is entropy. Biology is the triumph of conserving entropy at the expense of energy.

      There are probably a large number of undiscovered biology processes that rely upon quantum effects.

      The most prominent example I will mention for information, is the charge separation that occurs in your eyes, you are reading this with ;-)

      • (Score: 0) by Anonymous Coward on Saturday September 22 2018, @08:53PM

        by Anonymous Coward on Saturday September 22 2018, @08:53PM (#738647)

        Some people are using screen readers... Does charge separation still occur in their eyes?

    • (Score: 0) by Anonymous Coward on Saturday September 22 2018, @08:37PM (4 children)

      by Anonymous Coward on Saturday September 22 2018, @08:37PM (#738644)

      externally (to the photon), duh.

      how can you get "into" the reference frame of a photon?

      the photon is "absorbed" by the electron cloud. the energy perturbs the electrons, until one is perturbed enough to move up to a higher orbit. the new state is not stable, so it "relaxes", and the released energy is as another photon. these transitions all take time, breathtakingly small amounts, but not instantaneous.
      .

      • (Score: 0) by Anonymous Coward on Saturday September 22 2018, @08:47PM (2 children)

        by Anonymous Coward on Saturday September 22 2018, @08:47PM (#738645)

        My point was that there is no reference frame by which to measure time in QM. If you use GR, you need to pick one but now you are assuming two mutually exclusive theories to be correct.

        • (Score: 0) by Anonymous Coward on Sunday September 23 2018, @04:31AM (1 child)

          by Anonymous Coward on Sunday September 23 2018, @04:31AM (#738766)

          actually, there is. we cannot "get out of" our reference frame w.r.t photons (or get into theirs). we certainly can imagine doing so, and have maths and all sorts of computer sinulations to try and represent doing so, but we are kind of stuck in our own reference frames.

          we can certainly see effects of reference frame differences (Mercury's classical vs relativity-adjusted orbit time, a particular nuclear decay rate (muon decay?) that was funally explained whwn taking relativistic effects into account, etc.) but not photons, unless cerenkov radiation is a form of it...

          that being said, what happens "inside" a photon that is locked in a photon trap? does time keep advancing inside it (or is it even relevant...)?

          • (Score: 0) by Anonymous Coward on Sunday September 23 2018, @12:38PM

            by Anonymous Coward on Sunday September 23 2018, @12:38PM (#738823)

            All that math and computer simulation you refer to assumes GR is correct... which means assuming QM is incorrect. So basically they can conclude whatever they want since theres a contradiction in the logic.

      • (Score: 0) by Anonymous Coward on Sunday September 23 2018, @03:08PM

        by Anonymous Coward on Sunday September 23 2018, @03:08PM (#738860)

        could one also argue that the measured times is the time the electron needs to "absorb" the photon, but once does, jumps instantaneously?
        so the measured time is the time the photon needs to convince the electron to wholly interact with it?

  • (Score: 0) by Anonymous Coward on Sunday September 23 2018, @12:48AM

    by Anonymous Coward on Sunday September 23 2018, @12:48AM (#738705)

    (Units still to be determined)

  • (Score: 0) by Anonymous Coward on Sunday September 23 2018, @11:35PM

    by Anonymous Coward on Sunday September 23 2018, @11:35PM (#739001)

    "quantum ... observe ... measure ... precisely"

    Found the folks working on the Heisenberg Compensators. Anybody know if they've taken an interest in the whale population leately?

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